The present invention relates to a variable displacement swash plate compressor.
Japanese Laid-Out Patent Publication Nos. 5-172052 and 52-131204 describe conventional variable displacement swash plate compressors (hereafter simply referred to as the compressors). The compressors each have a housing including a suction chamber, a discharge chamber, a swash plate chamber, and cylinder bores. A rotatable drive shaft is supported in the housing. A swash plate that is rotatable together with the drive shaft is arranged in the swash plate chamber. A link mechanism is located between the drive shaft and the swash plate to allow the inclination angle of the swash plate to change. The inclination angle refers to an angle relative to a direction orthogonal to the rotation axis of the drive shaft. Each cylinder bore accommodates a piston. The piston, which is reciprocated in the cylinder bore, defines a compression chamber in the cylinder bore. A conversion mechanism coverts rotation of the swash plate to reciprocation of the piston in each cylinder bore. The stroke when the piston reciprocates is in accordance with the inclination angle of the swash plate. The inclination angle of the swash plate is changed by an actuator, which is controlled by a control mechanism.
In the compressor described in Japanese Laid-Out Patent Publication No. 5-172052, each cylinder bore is formed in a cylinder block, which is an element of the housing, and includes a first cylinder bore, which is located at a front side of the swash plate, and a second cylinder bore, which is located at a rear side of the swash plate. Each piston includes a first head, which reciprocates in the first cylinder bore, and a second head, which is formed integrally with the first head and which reciprocates in the second cylinder bore.
The compressor includes a pressure regulation chamber in a rear housing member, which is an element of the housing like the cylinder block. In addition to the cylinder bores, the cylinder block includes a control pressure chamber, which is in communication with the pressure regulation chamber. The control pressure chamber is located at the same side as the second cylinder bores, that is, the rear side of the swash plate. The actuator, which is located in the control pressure chamber, is not rotated integrally with the drive shaft. More specifically, the actuator includes a non-rotation movable body that covers the rear end of the drive shaft. The non-rotation movable body includes an inner wall surface that supports the rear end of the drive shaft so that the rear end is rotatable. The non-rotation movable body is movable along the rotation axis of the drive shaft. Although the non-rotation movable body moves in the control pressure chamber along the rotation axis of the drive shaft, the non-rotation movable body is not allowed to rotate about the rotation axis of the drive shaft. A spring that urges the non-rotation movable body toward the front is arranged in the control pressure chamber. The actuator includes a movable body, which is coupled to the swash plate and movable along the rotation axis of the drive shaft. A thrust bearing is arranged between the non-rotation movable body and the movable body. A pressure control valve, which changes the pressure of the control pressure chamber, is arranged between the pressure regulation chamber and the discharge chamber. A change in the pressure of the control pressure chamber moves the non-rotation movable body and the movable body in the axial direction of the drive shaft.
A link mechanism includes a movable body and a lug arm, which is fixed to the drive shaft and located at a first side of the swash plate. The movable body includes a first elongated hole, which extends in a direction orthogonal to the rotation axis of the drive shaft and in a direction from a circumferential side toward the rotation axis of the drive shaft. The lug arm includes a second elongated hole, which extends in a direction orthogonal to the rotation axis of the drive shaft and in a direction from a circumferential side toward the rotation axis of the drive shaft. The swash plate includes a first arm, which is located on the rear side and which extends toward the second cylinder bores, and a second arm, which is located on the front side and which extends toward the first cylinder bores. A first pin is inserted through the first elongated hole to couple the swash plate and the movable body so that the first arm is pivotally supported about the first pin relative to the movable body. A second pin is inserted through the second elongated hole to couple the swash plate and the lug arm so that the second arm is pivotally supported about the second pin relative to the lug arm. The first pin extends parallel to the second pin. The first and second pins are inserted through the first and second elongated holes so that the first and second pins are located at opposite sides of the drive shaft in the swash plate chamber.
In this compressor, the pressure control valve opens to connect the discharge chamber and the pressure regulation chamber so that the pressure of the control pressure chamber becomes higher than that of the swash plate chamber. This moves the non-rotation movable body and the movable body toward the front. Thus, the movable body pivots the first arm of the swash plate about the first pin and pushes the swash plate. Simultaneously, the lug arm pivots the second arm of the swash plate about the second pin. More specifically, the movable body pivots the swash plate using the first pin, which is where the swash plate and the movable body are coupled, as an action point, and the second pin, which is where the swash plate and the lug arm are coupled, as a fulcrum point. In this manner, the inclination angle of the swash plate increases in the compressor, lengthens the stroke of the pistons, and increases the compressor displacement for each rotation of the drive shaft.
When the pressure control valve closes to disconnect the discharge chamber and the pressure regulation chamber, the pressure of the control pressure chamber becomes low and about the same as that of the swash plate chamber. This moves the non-rotation movable body and the movable body toward the rear. Thus, the movable body pivots the first arm of the swash plate about the first pin and pulls the swash plate. Simultaneously, the lug arm pivots the second arm of the swash plate about the second pin. In this manner, the inclination angle of the swash plate decreases in the compressor, shortens the stroke of the pistons, and decreases the compressor displacement for each rotation of the drive shaft.
In the compressor of Japanese Laid-Open Patent Publication No. 52-131204, the actuator is rotatable integrally with the drive shaft in the swash plate chamber. More specifically, the actuator includes a partitioning body fixed to the drive shaft. The partitioning body accommodates a movable body, which is movable relative to the partitioning body along the rotation axis. A control pressure chamber is defined between the partitioning body and the movable body to move the movable body with the pressure of the control pressure chamber. A communication passage, which is in communication with the control pressure chamber, extends through the drive shaft. A pressure control valve is arranged between the communication passage and the discharge chamber. The pressure control valve is configured to change the pressure of the control pressure chamber and move the movable body relative to the partitioning body along the rotation axis. The movable body includes a rear end that is in contact with a hinge ball. The hinge ball, which is located in the central portion of the swash plate, pivotally couples the swash plate to the drive shaft. A pushing spring, which urges the hinge ball in the direction that increases the inclination angle of the swash plate, is arranged at the rear end of the hinge ball.
A link mechanism includes the hinge ball and an arm, which is located between the partitioning body and the swash plate. The pushing spring urges the hinge ball from the rear and holds the hinge ball in contact with the partitioning body.
A first pin, which extends in a direction orthogonal to the rotation axis, is inserted through the front end of the arm. The first pin couples the arm and the partitioning body. The front end of the arm is pivotal about the first pin relative to the partitioning body. Further, a second pin, which extends in a direction orthogonal to the rotation axis, is inserted through the rear end of the arm. The rear end of the arm is pivotal about the second pin relative to the swash plate. In this manner, the arm and the first and second pins couple the swash plate and the partitioning body.
In this compressor, the pressure control valve opens to connect the discharge chamber and the pressure regulation chamber so that the pressure of the control pressure chamber becomes higher than that of the swash plate chamber. This moves the movable body toward the rear and pushes the hinge ball toward the rear against the urging force of the pushing spring. The arm is pivoted about the first and second pins. Thus, the movable body pivots the swash plate using the location where the movable body pushes the hinge ball as an action point and the location where the swash plate and the partitioning body are coupled, that is, the two ends of the arm through which the first and second pins are inserted, as fulcrum points. In this manner, the inclination angle of the swash plate decreases in the compressor, shortens the stroke of the pistons, and decreases the compressor displacement for each rotation of the drive shaft.
When the pressure control valve closes to disconnect the discharge chamber and the pressure regulation chamber, the pressure of the control pressure chamber becomes low and about the same as that of the swash plate chamber. This moves the movable body toward the front, and the hinge ball follows the movable body due to the urging force of the pushing spring. Thus, the swash plate pivots in a direction opposite to the direction that decreases the inclination angle of the swash plate. The increase in the inclination angle lengthens the stroke of the pistons.
In a variable displacement swash plate compressor that uses an actuator such as that described above, high controllability is required for displacement control.
In this regard, with the compressor described in Japanese Laid-Open Patent Publication No. 5-172052, the partitioning body moves the movable body forward along the axis of the drive shaft with the thrust bearing. Thus, deformation of the thrust bearing would hinder efficient and prompt transmission of force. Thus, in this compressor, it may become difficult to change the inclination angle of the swash plate properly. In such a case, the displacement may not be controlled in the optimal manner when lengthening or shortening the piston stroke.
In the compressor described in Japanese Laid-Open Patent Publication No. 52-131204, the hinge ball is arranged at the central portion of the swash plate. Thus, the action point when changing the inclination angle of the swash plate is located near the central portion of the swash plate. As a result, the action point is located in the proximity of the fulcrum point in this compressor. This results in the compressor requiring a large force when the movable body pushes the hinge ball. Accordingly, in this compressor, it may also become difficult to change the inclination angle of the swash plate and control the displacement control in the optimal manner.